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<div class="moz-cite-prefix">Hi,<br>
<br>
Robert Bruninga wrote;<br>
<blockquote type="cite"><span
style="font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US">19k2
is there – the modules are $40</span></blockquote>
Bob, could you please post a link to these modules?<br>
<br>
<br>
Re: faster than 9k6 without modifying radios<br>
At the penalty of increased sensitivity to noise, modulations more
complex than K9NG/G3RUH can be fed through the <u>linear</u><u>
audio channel</u> of a pair of 9k6-ready ham transceivers. A 9k6
audio channel provides 5 kHz bandwidth, more than that of a
standard telephone land-line - a quick back of the envelope with
Shanon's Law indicates that we should be able to push bits much
faster than 9k6 <a
href="https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theorem"><a class="moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theorem">https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theorem</a></a><br>
Think DSP "TNC" software running in your PC, smartphone, Raspberry
pi, or in a processor like a PIC32 or STM32, with automatic
channel equalisation, GMSK/QPSK/n-QAM and Forward Error
Correction. Note that about twenty years ago you could just go to
the computer store and buy a consumer modem that would push 33k6
in 3.4 kHz BW down a (then) 40 year old telephone line...<br>
<br>
<br>
Re: Utilising smartphones, tablets, laptops, etc as user
interfaces;<br>
Why not use Bluetooth to link your device to the TNC? - it is
pretty much well universally supported by mobile devices and
doesn't chew through as much battery power as WiFi<br>
eg <a href="http://www.mobilinkd.com/tnc2/">http://www.mobilinkd.com/tnc2/</a><br>
<br>
<br>
Re: Transferring (larger) files;<br>
Send larger packets so there is less time consumed per unit
payload on TXdelay, ACK, etc. eg a 1500 byte/12kbit packet takes
less than 1.5 seconds to send at 9k6, and only incurs one TXdelay,
where as, if you limit yourself to 256 byte AX.25 packets, you
need to send 6 of them to move 1500 bytes... <br>
Forward Error Correction seems like a good way to reduce packet
re-transmissions (corruption of a single bit in standard AX.25
results in rejection of the packet, requiring a resend) <a
href="http://www.stensat.org/docs/FX-25_01_06.pdf"><a class="moz-txt-link-freetext" href="http://www.stensat.org/docs/FX-25_01_06.pdf">http://www.stensat.org/docs/FX-25_01_06.pdf</a></a><br>
New data transfer protocols eg using a "Fountain Code" would allow
most of the ACK/REJ packets to be eliminated and would be very
efficient for simultaneously distributing a file to multiple
recipients <a
href="https://docs.switzernet.com/people/emin-gabrielyan/060112-capillary-references/ref/MacKay05.pdf"><a class="moz-txt-link-freetext" href="https://docs.switzernet.com/people/emin-gabrielyan/060112-capillary-references/ref/MacKay05.pdf">https://docs.switzernet.com/people/emin-gabrielyan/060112-capillary-references/ref/MacKay05.pdf</a></a><br>
<br>
<br>
73 ZL2WRW<br>
Ross Whenmouth<br>
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